| W. S. McCormack | |
| Office1: | Lieutenant Governor of Montana |
| Term1: | 1925 - 1929 |
| Governor1: | John E. Erickson |
| Predecessor1: | Nelson Story, Jr. |
| Successor1: | Frank A. Hazelbaker |
| Office2: | Member of the Montana House of Representatives |
| Birth Name: | William Samuel McCormack |
| Birth Date: | 10 November 1863 |
| Birth Place: | Chicago, Illinois, U.S. |
| Death Place: | en route to California |
| Party: | Republican |
| Occupation: | Businessman, farmer |
| Residence: | Kalispell, Montana |
William Samuel McCormack (November 10, 1863 - September 5, 1946) was an American politician in the state of Montana who served as Lieutenant Governor of Montana from 1925 to 1929.[1] McCormack, who lived in Kalispell, Montana, was a farmer and businessman. He also served in the Montana House of Representatives.[2]